Apparatus and methods for treating tissue

ABSTRACT

Apparatus and methods are provided for thermally or mechanically treating tissue, such as valvular structures, to reconfigure or shrink the tissue in a controlled manner, thereby improving or restoring tissue function. The apparatus comprises a catheter in communication with an end effector. The end effector induces a temperature rise in an annulus of tissue surrounding the leaflets of a valve sufficient to cause shrinkage of the tissue, thereby reducing a diameter of the annulus and causing the valves to close more tightly. Alternatively, the end effector selectively induces a temperature rise in the chordae tendineae sufficient to cause a controlled degree of shortening of the chordae tendineae, thereby enabling the valve leaflets to be properly aligned. In another alternative, the end effector is configured to mechanically shorten the effective length of the chordae tendineae by forcing the tendineae through a tortuous path, again properly aligning the valve leaflets.

REFERENCE TO RELATED APPLICATIONS

The present application claims benefit from the filing date ofprovisional U.S. patent application Ser. No. 60/141,077 filed Jun. 25,1999.

FIELD OF THE INVENTION

The present invention relates to treatment of tissue. More particularly,the present invention provides methods and apparatus for treatingvalvular disease with a catheter inserted into a patient's cardiacchambers, the catheter having an end effector for modifying cardiacstructures, including valve leaflets and support structure.

BACKGROUND OF THE INVENTION

Degenerative valvular disease is the most common cause of valvularregurgitation in human beings. Regurgitation is typically characterizedby an expanded valve annulus or by lengthened chordae tendineae. Ineither case, an increase in the geometry of a valve or its supportingstructure causes the valve to become less effective, as it no longerfully closes when required.

Loose chordae tendineae may result, for example, from ischemic heartdisease affecting the papillary muscles. The papillary muscles attach tothe chordae tendineae and keep the leaflets of a valve shut. Some formsof ischemic cardiac disease cause the papillary muscles to lose theirmuscle tone, resulting in a loosening of the chordae tendineae. Thisloosening, in turn, allows the leaflets of the affected valve toprolapse, causing regurgitation.

It therefore would be desirable to provide methods and apparatus fortreatment of tissue that modify the geometry and operation of a heartvalve.

It would also be desirable to provide methods and apparatus that areconfigured to thermally treat chordae tendineae, the annulus of a valve,or valve leaflets.

SUMMARY OF THE INVENTION

In view of the foregoing, it is an object of the present invention toprovide methods and apparatus for the treatment of tissue that modifythe geometry and operation of a heart valve.

It is another object of the present invention to provide methods andapparatus that are configured to thermally treat chordae tendineae, theannulus of a valve, or valve leaflets.

These and other objects of the present invention are accomplished byproviding apparatus and methods for thermally or mechanically treatingtissue, such as valvular structures, to reconfigure or shrink the tissuein a controlled manner, thereby improving or restoring tissue function.Embodiments of the present invention advantageously may be employed tomodify flow regulation characteristics of a cardiac valve or itscomponent parts, as well as to modify flow regulation in other lumens ofthe body, including, for example, the urinary sphincter, digestivesystem valves, leg vein valves, etc., where thermal shrinkage ormechanical reconfiguration of tissue may provide therapeutic benefit.

In a first family of embodiments of the present invention, apparatus isprovided having an end effector that induces a temperature rise in anannulus of tissue surrounding the leaflets of a valve sufficient tocause shrinkage of the tissue, thereby reducing a diameter of theannulus and causing the valves to close more tightly. In a second familyof embodiments, apparatus is provided having an end effector thatselectively induces a temperature rise in the chordae tendineaesufficient to cause a controlled degree of shortening of the chordaetendineae, thereby enabling the valve leaflets to be properly aligned.In yet a third family of embodiments, apparatus is provided having anend effector comprising a mechanical reconfigurer configured to attachto a longitudinal member, such as the chordae tendineae. Thereconfigurer forces the longitudinal member into a tortuous path and, asa result, reduces the member's effective overall or straight length.

Any of these embodiments may employ one or more expanding members thatserve to stabilize the end effector in contact with the tissue orstructure to be treated. In addition, where it is desired to preservethe interior surface of a lumen or structure, the instrument may includemeans for flushing the surface of the tissue with cooled saline. Whereit is desired to achieve a predetermined degree of heating at a depthwithin a tissue or structure, the end effector may comprise a laserhaving a wavelength selected to penetrate tissue to the desired depth,or the end effector may comprise a plurality of electrically conductiveneedles energized by an RF power source, as is known in theelectrosurgical arts. The end effector may alternatively comprise anacoustic heating element, such as an ultrasonic transducer.

Methods of using apparatus according to the present invention are alsoprovided.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects and advantages of the present invention willbe apparent upon consideration of the following detailed description,taken in conjunction with the accompanying drawings, in which likereference numerals refer to like parts throughout, and in which:

FIG. 1 is a side-sectional view of a human heart showing majorstructures of the heart, including those pertaining to valvulardegeneration;

FIG. 2 is a side view of apparatus of a first family of embodimentsconstructed in accordance with the present invention;

FIGS. 3A-3C are, respectively, a side view of an end effector for usewith the apparatus of FIG. 2 and a sectional view through its catheteralong sectional view line A—A, a side view of an alternative endeffector and a sectional view of its catheter along view line B—B, and aside view of a still further alternative end effector;

FIG. 4 is a sectional view through the human heart, depicting a methodof using the apparatus of FIG. 2 to shrink tissue in an annulussurrounding the leaflets of a regurgitating valve;

FIGS. 5A and 5B are schematic views of alternative embodiments of theapparatus of FIG. 2;

FIGS. 6A-6D are views of a still further alternative embodiment of theapparatus of FIG. 2 having barbs, and illustrating a method of use;

FIGS. 7A-7C are schematic views showing, respectively, an alternativeembodiment of the end effector of FIGS. 6 having electrically insulatedbarbs, a method of using the end effector to thermally treat tissue, anda temperature profile within the tissue during treatment;

FIGS. 8A and 8B are side views of another alternative embodiment of theapparatus of FIG. 6 having multipolar, individual electrodes;

FIG. 9 is a side view of an alternative embodiment of the apparatus ofFIG. 8 having individual ultrasonic transducers;

FIG. 10 is a side-sectional view of another alternative embodiment ofthe apparatus of FIG. 8 having individual laser fibers;

FIG. 11 is a side-sectional view of an alternative embodiment of theapparatus of FIGS. 8-10 having individual barb members that may comprisemultipolar electrodes, ultrasonic transducers, or laser fibers;

FIG. 12 is a sectional view through the human heart, illustrating analternative method of introducing apparatus of the first family ofembodiments to a treatment site;

FIGS. 13A and 13B are views of an alternative embodiment of theapparatus of FIG. 2 shown, respectively, in schematic side view and inuse shrinking an annulus of tissue;

FIGS. 14A and 14B are, respectively, a side view of an alternativeembodiment of the apparatus of FIG. 2, and a method of using theembodiment via the introduction technique of FIG. 12;

FIGS. 15A and 15B are isometric views of an alternative end effector foruse with the apparatus of FIGS. 14;

FIG. 16 is a top view of apparatus of a second family of embodimentsconstructed in accordance with the present invention;

FIGS. 17A-17C are views of end effectors for use with the apparatus ofFIG. 16;

FIG. 18 is a sectional view of the human heart, illustrating a method ofusing the apparatus of FIG. 16 to selectively induce a temperature risein the chordae tendineae sufficient to cause a controlled degree ofshortening of the tendineae;

FIGS. 19A-19C show a section of chordae tendineae and illustrate amethod of shrinking the tendineae in a zig-zag fashion using the endeffector of FIG. 17C with the apparatus of FIG. 16;

FIGS. 20A-20C show, respectively, a side view of an intact tendineae, aside view of the tendineae after treatment by a shrinkage technique, anda cross section through the tendineae along sectional view line C—C ofFIG. 20A after treatment by an alternative shrinkage technique;

FIGS. 21A and 21B are side views of apparatus of a third family ofembodiments, constructed in accordance with the present invention, shownin a collapsed delivery configuration and in an expanded deployedconfiguration;

FIGS. 22A and 22B are schematic views depicting a method of using theapparatus of FIGS. 21 to mechanically shorten an effective length ofchordae tendineae; and

FIG. 23 is a side view, partially in section, illustrating a method andapparatus for non-invasive coagulation and shrinkage of scar tissue inthe heart, or shrinkage of the valve structures of the heart.

DETAILED DESCRIPTION OF THE INVENTION

With reference to FIG. 1, a sectional view through human heart H ispresented. Major structures labeled include the right atrium RA, leftatrium LA, right ventricle RV, left ventricle LV, superior vena cavaSVC, inferior vena cava IVC, and ascending aorta AA. Structures that maybe involved in valvular degeneration and regurgitation are also labeled,including the papillary muscles PM, chordae tendineae CT, valve leafletsL, and annuluses of tissue surrounding the leaflets A, as well as thetricuspid valve TV, the bicuspid or mitral valve MV, and the aorticvalve AV. The pulmonary valve PV is not seen in the cross section ofFIG. 1, but may also experience valvular degeneration. As discussedpreviously, degenerative valvular disease often leads to valvularregurgitation, which is typically characterized by an expanded valveannulus A or by lengthened chordae tendineae CT. Loose chordae tendineaemay result from ischemic heart disease affecting the papillary musclesPM, which attach to the chordae tendineae and act to regulate flowthrough leaflets L.

The present invention therefore provides apparatus and methods forshrinking or reconfiguring tissue, such as annulus A or chordaetendineae CT. Embodiments of the present invention advantageously may beemployed to modify flow regulation characteristics of a cardiac valve orits component parts, as well as to modify flow regulation in otherlumens of the body, including, for example, the urinary sphincter,digestive system valves, leg vein valves, etc., where thermal shrinkageor mechanical reconfiguration of tissue may provide therapeutic benefit.

FIGS. 2-15 illustrate apparatus of a first family of embodiments of thepresent invention. The first family of embodiments have an end effectorthat induces a temperature rise in an annulus of tissue surrounding theleaflets of a valve sufficient to cause shrinkage of the tissue, therebyreducing a diameter of the annulus and causing the valve to close moretightly.

Referring to FIG. 2, apparatus 30 comprises catheter 32 having endeffector 34 in a distal region of the catheter. End effector 34 may becollapsible within and extendable beyond the distal end of catheter 30to permit percutaneous delivery to a treatment site. End effector 34 hasan annular shape to facilitate treatment of an annulus of tissue, aswell as stabilization against the walls of a treatment site.

With reference to FIGS. 3A-3C, alternative embodiments of end effector34 and catheter 32 are described. In FIG. 3A, end effector 34 comprisesexpandable balloon 40. Balloon 40 comprises bipolar electrodes 42 a and42 b that may be attached to a radiofrequency (“RF”) voltage or currentsource (not shown). Balloon 40 further comprises lumen 44 to facilitateunimpeded blood flow or fluid transport therethrough, and temperaturesensors 46 to monitor shrinkage of tissue caused by current flow betweenbipolar electrodes 42 a and 42 b. Sensors 46 may comprise, for example,standard thermocouples, or any other temperature sensor known in theart.

The end effector of FIG. 3A is thus capable of achieving controlledluminal shrinkage while allowing blood to pass through the center ofballoon 40. Electrodes 42 a and 42 b are disposed as bands on theperiphery of balloon 40 and may inject an RF electrical current into thewall of a treatment site, such as an annulus or lumen, to shrinkcollagen contained therein. Furthermore, balloon 40 may be inflated witha circulating coolant C, such as water, to cool the surface of balloon40 and thereby minimize thermal damage at the surface of the treatmentsite. Thermally damaged tissue may be thrombogenic and may form thrombuson its surface, leading to potentially lethal complications.

FIG. 3A also provides a cross section through an embodiment of catheter32, along sectional view line A—A, for use in conjunction with theballoon embodiment of end effector 34. Catheter 32 comprises coolantlumens 48 a and 48 b that may circulate coolant C into and out ofballoon 40, respectively. It further comprises wires 49 a-49 c,electrically coupled to electrode 42 a, electrode 42 b, and temperaturesensors 46, respectively.

In FIG. 3B, an alternative embodiment of end effector 34 and catheter 32is presented. Instead of RF energy, the heating element in thisembodiment is a laser source (not shown) coupled to fiber optic cable 50having side firing tip 51. The laser source injects light energy intothe wall of a treatment site via fiber optic cable 50, thereby thermallyshrinking the tissue. The wavelength of the laser may be selected topenetrate tissue to a desired depth. Furthermore, a plurality of fiberoptic cables 50, coupled to the laser source and disposed about thecircumference of balloon 40, may be provided.

Balloon 40 is substantially transparent to the laser energy, and coolantC may again serve to cool the surface of balloon 40, thereby minimizingdamage at the surface of the treatment site. The circulating stream ofcoolant C maintains the temperature of surface tissue layers at asufficiently low level to prevent thermal damage, and thus, to preventformation of thrombus. Temperature sensor 46 optionally may also beprovided.

As seen in FIG. 3C, end effector 34 may alternatively comprise wrappedsheet 52 incorporating one or more electrodes on its surface. Sheet 52may be advanced to a treatment site in a collapsed deliveryconfiguration within a lumen of catheter 32, and may then be unfurled toan expanded deployed configuration wherein it contacts the interior wallof the treatment site and may be energized to shrink tissue.

Referring now to FIG. 4, a method of using apparatus 30 to thermallyshrink an annulus of tissue is described. End effector 34 is placed inintimate contact with the inner wall of a blood vessel or other bodylumen. In the valvular regurgitation treatment technique of FIG. 4, endeffector 34 is percutaneously delivered just proximal of aortic valve AVwithin ascending aorta AA at annulus of tissue A supporting leaflets L,using well-known techniques. Aortic valve AV suffers from valvulardegeneration, leading to regurgitation. End effector 34 delivers energyto annulus A sufficient to heat and shrink the annulus, thus enhancingfunction of the degenerative valve. Collagen within annulus A shrinksand reduces a diameter of the annulus. Leaflets L are approximatedtowards one another, as seen in dashed profile in FIG. 4, and valvularregurgitation is reduced or eliminated. In addition to valvularregurgitation, the technique is expected to effectively treat aorticinsufficiency.

End effector 34 stabilizes apparatus 30 against the wall of a bodypassageway. Once stabilized, a source of energy may be applied to thewall to thermally shrink the tissue contained in the wall. In additionto the application of FIG. 4, treatment may be provided, for example, tothe annulus of mitral valve MV, to the urinary sphincter for treatmentof incontinence, to digestive system valves for treatment of acidreflux, to leg vein valves, and to any other annulus of tissue wheretreatment is deemed beneficial.

With reference to FIGS. 5A and 5B, alternative embodiments of theapparatus of FIG. 2 are described. In FIG. 5A, apparatus 60 comprisescatheter 62 having a lumen, in which end effector 64 is advanceablydisposed. End effector 64 comprises monopolar electrode 66, which isfabricated in an arc from a shape memory alloy, such as spring steel ornitinol, to approximate the shape of an annulus of tissue at a treatmentsite within a patient. Electrode 66 may be retracted within the lumen ofcatheter 62 to facilitate transluminal, percutaneous delivery to thetreatment site. Once in position, electrode 66 may be advanced out of adistal region of catheter 62. The electrode resumes its arc shape andapproximates the wall of the treatment site.

Monopolar electrode 66 is electrically coupled to RF source 68, which ispositioned outside of the patient. RF source 68 is, in turn, coupled toreference electrode 69. When RF source 68 is activated, current flowsbetween monopolar electrode 66 and reference electrode 69, which may,for example, be attached to the exterior of the patient in the region ofthe treatment site. RF current flows into the wall of the treatmentsite, thereby effecting annular tissue shrinkage, as describedpreviously.

In FIG. 5B, a bipolar embodiment is provided. Apparatus 70 comprisescatheter 72 and end effector 74. End effector 74 comprises a pluralityof atraumatic tipped legs 76 that are electrically coupled by aplurality of current carrying wires 78 to an RF source (not shown). Theplurality of legs contact the wall of a treatment site and injectcurrent into the wall. The current flows between the tips of the legs.Alternatively, the plurality of legs may comprise a monopolar electrodecoupled by a single wire to the RF source, and current may flow betweenthe plurality of legs and a reference electrode, as in FIG. 5A.

Referring to FIGS. 6A-6D, another alternative embodiment of theapparatus of FIG. 2 is described. FIG. 6A shows apparatus 80 inside-sectional view in a retracted delivery configuration. Apparatus 80comprises catheter 82 and end effector 84. Catheter 82 further comprisescentral bore 86, a plurality of side bores 88, and optional temperaturesensors 90. End effector 84 may, for example, be fabricated from nitinolor spring steel, and comprises conductive shaft 92 having a plurality ofradially extending electrodes 94 with optional barbs 96. Conductiveshaft 92 is electrically coupled to RF source 98, which is electricallycoupled to reference electrode 99. Conductive shaft 92 is disposedwithin central bore 86, while electrodes 94 are disposed within sidebores 88.

End effector 84 is advanceable with respect to catheter 82. Whenadvanced distally, apparatus 80 assumes the expanded deployedconfiguration of FIG. 6B, wherein electrodes 94 extend through sidebores 88 beyond the surface of catheter 82. Apparatus 80 is alsoconfigured such that its distal region may approximate the shape of anannulus of tissue, as described hereinbelow with respect to FIG. 6D, andis thus suited for both linear and circular subsurface tissuecoagulation and shrinkage.

FIGS. 6C and 6D provide a method of using apparatus 80 to treat annulusof tissue A surrounding a heart valve. Apparatus 80 is percutaneouslyadvanced to the surface of a heart valve in the delivery configurationof FIG. 6C. Once positioned at annulus A, the distal region of apparatus80 approximates the shape of the annulus, as seen in FIG. 6D. This maybe accomplished, for example, with a steering mechanism comprising twopurchase points or a pre-shaped tip that is retracted within a straightguiding catheter to allow insertion into the vascular system, asdescribed in U.S. Pat. No. 5,275,162, which is incorporated herein byreference. Once inserted, the pre-shaped tip is advanced out of theguide catheter and recovers its preformed shape.

With apparatus 80 approximating annulus A, end effector 84 is distallyadvanced with respect to catheter 82, thereby selectively advancingelectrodes 94 into the annulus. RF source 98 then provides RF current,which flows between electrodes 94 and reference electrode 99. Theannulus of tissue shrinks, bringing valve leaflets into proper positionand minimizing or eliminating regurgitation through the valve.

Catheter 82 insulates conductive shaft 92 from annulus A, therebyprotecting surface tissue and only allowing coagulation at depth intreatment zones surrounding electrodes 94. To further ensure thatcoagulation only occurs at depth, a coolant, such as saline, may beintroduced through central bore 86 and side bores 88 of catheter 82 tothe surface of annulus A, thereby cooling and flushing the area whereelectrodes 94 penetrate the tissue. It is expected that such liquidinfusion will keep the surface of the annulus clean and will preventthrombus formation in response to thermal damage.

Referring now to FIGS. 7A-7C, an alternative embodiment of end effector84 of FIGS. 6 is described. The end effector of FIGS. 7 is equivalent tothe end effector of FIGS. 6 except that it is coated with electricallyinsulating layer I. Insulation layer I covers the entire exterior of endeffector 84, except at the distal ends of the plurality of electrodes94. The layer is preferably sufficiently thin to allow insertion ofelectrodes 94 into tissue T without impediment. The exposed distal endsof the electrodes are configured to deliver energy into subsurfacetissue at treatment zones Z. The zones may be ideally modeled as spheresof subsurface tissue. Tissue shrinks within treatment zones Z withoutdamaging surface tissue, as seen in FIG. 7B.

The size of treatment zones Z may be controlled to ensure that tissueremodeling only occurs at depth. Assuming a temperature T₁, at whichtissue damage is negligible, the magnitude of current passed throughtissue T may be selected (based on the material properties of the tissueand the depth of insertion of electrodes 94 within the tissue) such thatthe temperature decays from a temperature T₀ at a position D₀ at thesurface of an electrode 94 to the benign temperature T₁ at a distance D₁from the surface of the electrode. The distance D₁ may be optimized suchthat it is below the surface of tissue T. An illustrative temperatureprofile across a treatment zone Z is provided in FIG. 7C.

With reference to FIGS. 8A and 8B, another alternative embodiment of theapparatus of FIG. 6 is described. Apparatus 100 comprises catheter 102and end effector 104. End effector 104 further comprises a plurality ofindividual, multipolar electrodes 106, which are electrically coupled toan RF or other current source (not shown) by a plurality of currentcarrying wires 108. As with the embodiments of FIGS. 6 and 7, apparatus100 is configured such that end effector 104 may approximate an annulus,as seen in FIG. 8B.

Referring to FIGS. 9-11, alternative embodiments of the apparatus ofFIGS. 8 are described. In FIG. 9, apparatus 110 comprises catheter 112and end effector 114. End effector 114 comprises a plurality of acousticheating elements 116. Acoustic elements 116 may, for example, compriseultrasonic transducers. The acoustic energy may further be focused byappropriate means, for example, by lenses, such that a tissue damagethreshold sufficient to cause shrinkage is only attained at a specifieddepth within treatment site tissue, thereby mitigating surface tissuedamage and thrombus formation. Acoustic elements 116 are connected toappropriate controls (not shown). Apparatus 110, and any other apparatusdescribed herein, may optionally comprise temperature sensors 118.

In FIG. 10, apparatus 120 comprises catheter 122 and end effector 124.Catheter 122 comprises a plurality of central bores 126 and a pluralityof side bores 128, as well as a plurality of optional temperaturesensors 130. End effector 124 comprises a plurality of side-firing fiberoptic laser fibers 132 disposed within central bores 126 of catheter122. The fibers are aligned such that they may deliver energy throughside bores 128 to heat and induce shrinkage in target tissue. Fibers 132are coupled to a laser source (not shown), as discussed with respect toFIG. 3B. Suitable wavelengths for the laser source preferably range fromvisible (488-514 nm) to infrared (0.9-10.6 microns), wherein eachwavelength has an ability to heat tissue to a predetermined depth. As anexample, a preferred laser source comprises a continuous wave laserhaving a 2.1 micron wavelength, which will shrink and heat tissue to adepth of 1-2 mm.

In FIG. 11, apparatus 140 comprises catheter 142 and end effector 144.Catheter 132 comprises central bores 146 and side bores 148. Catheter132 further comprises temperature sensors 150 that are configured topenetrate superficial tissue layers to measure temperature at depth.Temperature sensors 150 may be retractable and extendable to facilitatepercutaneous delivery of apparatus 140. End effector 144 comprisesfibers 152 disposed within central bores 146. Fibers 152 are retractablewithin and extendable beyond side bores 148. Fibers 152 are preferablysharpened to facilitate tissue penetration and energy delivery tosubsurface tissue, thereby inducing shrinkage of the tissue.

Fibers 152 may comprise any of a number of energy delivery elements. Forexample, fibers 152 may comprise a plurality of optical fibers coupledto a laser (not shown). The wavelength of the laser may be selected asdescribed hereinabove, while the energy deposited by the fibers may becontrolled responsive to the temperature recorded by sensors 150. Thus,for example, a controller (not shown) may be provided to switch off thelaser once a preset temperature, for example, 45° C.-75° C., isattained, thereby ensuring that a sufficiently high temperature isachieved to cause tissue shrinkage without inadvertently damagingsurrounding tissues.

Fibers 152 may alternatively comprise a plurality of multipolarelectrodes. Each electrode may be capable of injecting RF energy intotissue independently. Alternatively, current may be passed between apair of adjacent or non-adjacent electrodes to heat intervening tissue.

Referring now to FIG. 12, an alternative method of introducing apparatusof the first family of embodiments to a treatment site is described.Apparatus 30 of FIG. 2 is been introduced to the annulus of tissue Asurrounding mitral valve MV via the venous circulatory system. Catheter32 is transluminally inserted via the jugular vein and superior venacava SVC. The distal end of the catheter or a separate instrument thenpenetrates atrial septum AS using a procedure known as septostomy. Oncethe septum is perforated, end effector 34 may be inserted into leftatrium LA and positioned over mitral valve annulus A to effect thethermal treatment described hereinabove. The tricuspid valve in theright ventricle, and the pulmonic valve, may also be treated in the samemanner using a venous approach.

Referring to FIGS. 13A and 13B, a further alternative embodiment of theapparatus of FIG. 2 is described that may be introduced using thetechnique of FIG. 4, the technique of FIG. 12, or by another suitabletechnique. Apparatus 160 comprises catheter 162 and end effector 164.End effector 164 comprises adjustable, heatable loop 166, which isconfigured for dynamic sizing to facilitate positioning next to tissueat a treatment site. The size of loop 166 is adjusted so as to liecontiguous with annulus of tissue A at a treatment site, as seen in FIG.13B. The loop may be collapsible within catheter 162 to facilitatepercutaneous delivery and is electrically coupled to RF source 168,which is electrically coupled to reference electrode 170. Loop 166 maybe fabricated from nitinol, copper, or any other suitably conductive andductile material.

Referring to FIGS. 14A and 14B, a still further alternative embodimentof the apparatus of FIG. 2, and a method of using the embodiment withthe introduction technique of FIG. 12, is described. Apparatus 170comprises catheter 172 and end effector 174. End effector 174 is capableof grabbing and penetrating tissue, as well as delivering RF energy intotissue. End effector 174 comprises jaws 176 a and 176 b, which arespring-biased against one another to a closed position. By pushing aknob on the handpiece (not shown), the jaws may be actuated to an openposition configured to grab tissue at a treatment site. RF energy maythen be deposited in the tissue in a monopolar or bipolar mode. Jaws 176may optionally be coated with electrically insulating layer I everywhereexcept in a distal region, such that tissue is only treated at depth, asdescribed hereinabove. End effector 174 has temperature sensor 178 tocontrol power delivered to the tissue, again as described hereinabove.

With reference to FIG. 14B, a method of using apparatus 170 via aseptostomy introduction technique to treat mitral valve regurgitation isdescribed. In particular, jaws 176 of end effector 174 are actuated toengage individual sections of valve annulus A so as to penetrate intothe collagenous sublayers and to thermally shrink those sublayers. Theprocedure may be repeated at multiple locations around the perimeter ofannulus A until regurgitation is minimized or eliminated.

FIGS. 15A and 15B show an alternative end effector for use withapparatus 170 of FIGS. 14. End effector 180 is shown in an open positionand in a closed position, respectively, and comprises jaws 182 a and 182b. End effector 180 is similar to end effector 174, except that jaws 182are configured to engage tissue with a forceps grasping motion whereinbent tips 184 a and 184 b of the jaws are disposed parallel to oneanother and contact one another when closed.

With reference now to FIGS. 16-20, apparatus of a second family ofembodiments of the present invention are described. These embodimentsare provided with an end effector that selectively induces a temperaturerise in the chordae tendineae sufficient to cause a controlled degree ofshortening of the chordae tendineae, thereby enabling valve leaflets tobe properly aligned.

A preferred use for apparatus of the second family is in treatment ofmitral valve regurgitation. Mitral valve regurgitation has many causes,ranging from inherited disorders, such as Marphan's syndrome, toinfections and ischemic disease. These conditions affect themacromechanical condition of the mitral valve and prevent the valve fromclosing completely. The resulting gap in the leaflets of the valvepermit blood to regurgitate from the left ventricular chamber into theleft atrium.

Mechanically, the structural defects characterizing mitral valveregurgitation include: (1) the chordae tendineae are too long due to agiven disease state; (2) papillary muscle ischemia changes the shape ofthe papillary muscle, so that attached chordae tendineae no longer pullthe leaflets of the mitral valve completely shut; (3) the annulus of themitral valve becomes enlarged, resulting in the formation of a gapbetween the leaflets when closed; and (4) there is an inherent weaknessin the leaflets, leaving the leaflets floppy and dysfunctional.

In accordance with the principles of the present invention, atemperature rise is induced in the support structure of the mitral valveto cause shrinkage that modifies the geometry of the valve to restoreproper stopping of blood backflow and thereby regurgitation. Thisprocess is depicted in FIGS. 18-20 using the apparatus of FIGS. 16 and17 to selectively shrink portions of the chordae tendineae, therebybringing leaflets of the mitral valve leaflets into alignment. Apparatusof the second family may also be used in treatment of aortic valveregurgitation, and in treatment of a variety of other ailments that willbe apparent to those of skill in the art.

Referring to FIG. 16, apparatus 200 comprises catheter 202 and endeffector 204. Catheter 204 optionally comprises collapsible andexpandable stabilizer 206, configured to stabilize apparatus 200 in abody lumen. Stabilizer 206 may comprise, for example, struts or aninflatable balloon.

End effector 204 may be collapsible to a delivery configuration withincatheter 202, and may expand to a delivery configuration beyond a distalend of the catheter. End effector 204 is configured to engage, heat, andshrink chordae tendineae. Various sources of energy may be used toimpart heat to the collagenous tissue and thereby shrink it, includingRF energy, focused ultrasound, laser energy, and microwave energy. Inaddition, chemical modifiers, such as aldehydes, may be used. For laserembodiments, a preferred laser is a continuous wave Holmium:Yag laser,with application of visible or infrared laser energy in the wavelengthrange of 400 nanometers to 10.6 micrometers.

With reference to FIGS. 17A-17C, embodiments of end effector 204 aredescribed. In FIG. 17A, the end effector comprises a gripping mechanismthat carries the heating element. Arms 210 a and 210 b are opposing andspring-biased against each other. The arms may be actuated to an openposition using a handpiece (not shown) coupled thereto. Arms 210 a and210 b may alternatively be vertically displaced with respect to oneanother to allow the arms to criss-cross and tightly grasp tissue.Heating elements 212 and temperature sensors 214 are attached to thearms. Heating elements 212 may comprise electrodes, acoustictransducers, side-firing laser fibers, radioactive elements, etc. It maybe desirable to employ a saline flush with heating elements 212 toprevent coagulation of blood caught between arms 210.

FIG. 17B shows an embodiment of end effector 204 with fixed, straightarms 220 a and 220 b. The arms are configured to engage and disengagechordae tendineae simply by being positioned against the tendineae. FIG.17C shows an embodiment of the end effector having arms 230 a and 230 b.Multiple heating elements 212 are disposed on arm 230 a. When heatingelements 212 comprise bipolar electrodes, current flow through thetendineae using the embodiment of FIG. 17C may be achieved primarilyalong a longitudinal axis of the tendineae, as opposed to along a radialaxis of the tendineae, as will be achieved with the embodiment of FIG.17A. These alternative heating techniques are described in greaterdetail hereinbelow with respect to FIGS. 19 and 20.

Referring to FIG. 18, a method of using apparatus of the second familyof embodiments to induce shrinkage of chordae tendineae CT is described.Catheter 202 of apparatus 200 is advanced percutaneously, usingwell-known techniques, through the ascending aorta AA and aortic valveAV into the left ventricle LV, with end effector 204 positioned withinthe catheter in the collapsed delivery configuration. Stabilizer 206 isthen deployed to fix catheter 202 in ascending aorta AA, therebyproviding a stationary leverage point.

End effector 204 is expanded to the deployed configuration distal ofcatheter 202. The end effector is steerable within left ventricle LV tofacilitate engagement of chordae tendineae CT. End effector 204, as wellas any of the other end effectors or catheters described herein, mayoptionally comprise one or more radiopaque features to ensure properpositioning at a treatment site. End effector 204 is capable of movingup and down the chordae tendineae to grab and selectively singe certainsections thereof, as illustrated in dotted profile in FIG. 18, toselectively shorten chordae tendineae CT, thereby treating valvularregurgitation.

When energy is transmitted through tissue utilizing one of theembodiments of this invention, the tissue absorbs the energy and heatsup. It may therefore be advantageous to equip the end effector withtemperature or impedance sensors, as seen in the embodiments of FIGS.17, to output a signal that is used to control the maximum temperatureattained by the tissue and ensure that the collagen or other tissuesintended to be shrunk are heated only to a temperature sufficient forshrinkage, for example, a temperature in the range of 45° C.-75° C., andeven more preferably in the range of 55° C.-65° C. Temperatures outsidethis range may be so hot as to turn the tissue into a gelatinous massand weaken it to the point that it loses structural integrity. A closedloop feedback system advantageously may be employed to control thequantity of energy deposited into the tissue responsive to the output ofthe one or more sensors. In addition, the sensors may permit theclinician to determine the extent to which the cross-section of achordae has been treated, thereby enabling the clinician to heat treatonly a portion of the cross-section.

This technique is illustrated in FIGS. 19 and 20, in which alternatingbands, only a single side, or only a single depth of the chordae isshrunk to leave a “longitudinal intact fiber bundle.” This method may beadvantageous in that, by avoiding heat treatment of the entire crosssection of the chordae, there is less risk of creating mechanicalweakness.

FIGS. 19A-19C depict a method of shrinking a section of chordaetendineae CT in a zig-zag fashion using the embodiment of end effector204 seen in FIG. 17C. In FIG. 19A, the tendineae has an initialeffective or straight length L₁. Arms 230 engage chordae tendineae CT,and heating elements 212 are both disposed on the same side of thetendineae on arm 230 a. The heating elements may comprise bipolarelectrodes, in which case the path of current flow through tendineae CTis illustrated by arrows in FIG. 19A.

Collagen within the tendineae shrinks, and chordae tendineae CT assumesthe configuration seen in FIG. 19B. Treatment zone Z shrinks, and thetendineae assumes a shorter effective length L₂. Treatment may berepeated on the opposite side of the tendineae, as seen in FIG. 19C, sothat the tendineae assumes a zig-zag configuration of still shortereffective length L₃. In this manner, successive bands of treatment zonesZ and intact longitudinal fiber bundles may be established.

An additional pair of bipolar electrodes optionally may be disposed onarm 230 b of the end effector to facilitate treatment in bands onopposite sides of chordae tendineae CT. The depth of shrinkage attainedwith apparatus 200 is a function of the distance between the electrodes,the power, and the duration of RF energy application. If, laser energyis applied, the wavelengths of energy application may be selected toprovide only partial penetration of the thickness of the tissue. Forexample, continuous wave Holmium:YAG laser energy having a wavelength of2.1 microns penetrates a mere fraction of a millimeter and may be asuitable energy source.

FIGS. 20A-20C illustrate additional shrinkage techniques. Intact chordaetendineae CT is seen in FIG. 20A. FIG. 20B demonstrates shrinkage withapparatus 200 only on one side of the chordae, using the techniquedescribed with respect to FIGS. 19. FIG. 20C demonstrates shrinkagewith, for example the end effector of FIG. 17A or 17B, wherein, forexample, bipolar current flows across the tendineae and treats thetendineae radially to a certain preselected depth. When viewed incross-section along sectional view line C—C of FIG. 20A, chordaetendineae CT has an intact longitudinal fiber bundle core C surroundedby treatment zone Z.

With reference to FIGS. 21-22, apparatus of a third family ofembodiments of the present invention are described. These embodimentsare provided with an end effector comprising a mechanical reconfigurerconfigured to engage a longitudinal member, such as the chordaetendineae. The reconfigurer forces the longitudinal member into atortuous path and, as a result, reduces the member's effective overallor straight length.

Referring to FIGS. 21A and 21B, apparatus 300 comprises catheter 302 andend effector 304. End effector 304 comprises mechanical reconfigurer306, adapted to mechanically alter the length of a longitudinal member,for example, chordae tendineae. Reconfigurer 306 comprises a preshapedspring fabricated from a shape memory alloy, for example, nitinol,spring steel, or any other suitably elastic and strong material.Reconfigurer 306 is preshaped such that there is no straight paththrough its loops. Overlap between adjacent loops is preferablyminimized. The shape of reconfigurer 306 causes longitudinal members,such as chordae tendineae, passed therethrough to assume a zig-zagconfiguration and thereby be reduced in effective length. Reconfigurer306 is collapsible to a delivery configuration within catheter 302, asseen in FIG. 21A, and is expandable to a deployed configuration, as seenin FIG. 21B. The reconfigurer optionally may be selectively detachablefrom catheter 302.

With reference to FIGS. 22A and 22B, a method of using apparatus 300 tomechanically shorten chordae tendineae CT is described. Apparatus 300 isadvanced to the chordae tendineae, for example, using the techniquedescribed hereinabove with respect to FIG. 18. End effector 304 is thenexpanded from the delivery configuration seen in FIG. 22A to thedeployed configuration of FIG. 22B. Mechanical reconfigurer 306 regainsits preformed shape, and chordae tendineae CT is passed through atortuous path that reduces its effective length, thereby treatingvalvular regurgitation. Reconfigurer 306 may then be detached fromapparatus 300 and permanently implanted in the patient, or thereconfigurer may be left in place for a limited period of time tofacilitate complementary regurgitation treatment techniques.

Other embodiments of the third family in accordance with the presentinvention will be apparent to those of skill in the art in light of thisdisclosure.

Referring now to FIG. 23, apparatus in accordance with the presentinvention is described that may be used as either an embodiment of thefirst family or of the second family. Apparatus and methods are providedfor noninvasively coagulating and shrinking scar tissue around theheart, or valve structures inside the heart, using energy delivered viahigh intensity, focused ultrasound. Apparatus 350 comprises catheter 352and end effector 354. End effector 354 comprises ultrasonic transducer356 and focusing means 358, for example, a lens. Focused ultrasound ispropagated and directed with a high level of accuracy at the chordae CT,the annuluses A of the valves or at a section of bulging wall of theheart, using, for example, echocardiography or MRI for guidance. As withthe previous embodiments, the shrinkage induced by energy deposition isexpected to reduce valvular regurgitation. Apparatus 350 may also beused to reduce ventricular volume and shape, in cases where there isbulging scar tissue on the wall of the left ventricle LV secondary toacute myocardial infarction.

All of the above mentioned methods and apparatus may be used inconjunction with flow-indicating systems, including, for example, colorDoppler flow echocardiography, MRI flow imaging systems, or laserDoppler flow meters. Application of energy from the end effector may beselected such that regurgitation stops before the procedure iscompleted, as verified by the flow-indicating system. Alternatively, theprocedure may be “overdone” to compensate for expected tissue relapse,without compromising the ultimate outcome of the procedure.

Additionally, all of the foregoing apparatus and methods optionally maybe used in conjunction with ECG gating, thereby ensuring that tissue isat a specified point in the cardiac cycle before energy is depositedinto the tissue. ECG gating is expected to make treatment morereproducible and safer for the patient.

Although preferred illustrative embodiments of the present invention aredescribed above, it will be evident to one skilled in the art thatvarious changes and modifications may be made without departing from theinvention. It is intended in the appended claims to cover all suchchanges and modifications that fall within the true spirit and scope ofthe invention.

What is claimed is:
 1. Apparatus for treating tissue at a target site to modify flow through a valve, the apparatus comprising: a catheter having a distal end region, the catheter configured for transluminal delivery of the end region to the target site; and an end effector in communication with the distal end region, the end effector configured to approximate the shape of the tissue while transferring energy to the tissue at the target site to induce thermal shrinkage of collagen in the tissue, thereby modifying flow through the valve by reducing a circumference of the valve.
 2. The apparatus of claim 1, wherein the tissue at the target site comprises an annulus of tissue surrounding a cardiac valve.
 3. The apparatus of claim 2, wherein modifying flow through the valve comprises reducing a circumference of the cardiac valve.
 4. The apparatus of claim 1, wherein the tissue at the target site comprises a support structure of a cardiac valve.
 5. The apparatus of claim 4, wherein the support structure is chosen from the group consisting of a chordae tendineae and a papillary muscle.
 6. The apparatus of claim 5, wherein modifying flow through the valve comprises shortening the chordae tendineae to properly align leaflets of the valve.
 7. The apparatus of claim 1, wherein the tissue at the target site comprises a leaflet of a cardiac valve.
 8. The apparatus of claim 1 wherein the end effector comprises a temperature sensor.
 9. The apparatus of claim 8, wherein the temperature sensor is configured to penetrate tissue.
 10. The apparatus of claim 1, wherein the end effector comprises a tissue heating element.
 11. The apparatus of claim 9, wherein the tissue heating element is chosen from the group consisting of a monopolar electrode, a pair of bipolar electrodes, an acoustic transducer, a laser fiber coupled to a laser source, and a radiation source.
 12. The apparatus of claim 10, wherein the monopolar electrode is coupled to an RF source and a reference electrode.
 13. The apparatus of claim 10, wherein an RF source is coupled between the pair of bipolar electrodes.
 14. The apparatus of claim 1, wherein the end effector has a collapsed delivery configuration within a lumen of the catheter, and an expanded deployed configuration extending out of the lumen.
 15. The apparatus of claim 14, wherein the end effector is configured to penetrate tissue at the target site in the deployed configuration.
 16. The apparatus of claim 15, wherein the end effector further comprises an electrically insulating coating everywhere except at its distal end.
 17. The apparatus of claim 16, wherein the end effector is configured to approximate the shape of an annulus in the deployed configuration.
 18. The apparatus of claim 1, wherein the end effector comprises coolant to minimize surface tissue damage at the target site.
 19. The apparatus of claim 1, wherein the end effector comprises a saline flush.
 20. The apparatus of claim 1, wherein the catheter further comprises a stabilizer configured to stabilize the catheter within a body lumen.
 21. The apparatus of claim 1, wherein the end effector is configured to engage tissue.
 22. The apparatus of claim 1, wherein the end effector comprises an expandable balloon.
 23. The apparatus of claim 1, wherein the end effector comprises a wrapped sheet.
 24. The apparatus of claim 1, wherein the end effector comprises an atraumatic tipped leg.
 25. The apparatus of claim 1, wherein the end effector comprises a mechanical reconfigurer.
 26. The apparatus of claim 1, wherein the end effector comprises barbs.
 27. The apparatus of claim 1, wherein the end effector comprises an adjustable, heatable loop.
 28. The apparatus of claim 1, wherein the end effector comprises jaws.
 29. The apparatus of claim 1, wherein the end effector comprises arms.
 30. The apparatus of claim 1, further comprising a flow-indicating system in communication with the end effector.
 31. The apparatus of claim 30, wherein the flow-indicating system is chosen from the group consisting of a color Doppler flow echocardiography system, an MRI flow imaging system, and a laser Doppler flow meter.
 32. The apparatus of claim 1, further comprising an ECG gating system in communication with the end effector.
 33. A method for altering flow through a valve, the method comprising: providing apparatus comprising a catheter having a distal end region, and an end effector in communication with the end region; transluminally positioning the end effector in communication with tissue at a treatment site in the vicinity of the valve such that the end effector approximates a shape of the tissue; and transferring energy from the end effector to the tissue at the treatment site to shrink collagen in the tissue, thereby altering flow through the valve by reducing a circumference of the valve.
 34. The method of claim 33, wherein the treatment site is chosen from the group consisting of an annulus of tissue surrounding a cardiac valve, a support structure of a cardiac valve, a leaflet of a cardiac valve, a chordae tendineae of a cardiac valve, a papillary muscle, a urinary sphincter, a digestive system valve, and a leg vein valve.
 35. The method of claim 33, wherein transferring energy from the end effector to the tissue comprises transferring radiofrequency energy to the tissue.
 36. The method of claim 33, wherein transferring energy from the end effector to the tissue comprises transferring acoustic energy to the tissue.
 37. The method of claim 33, wherein transferring energy from the end effector to the tissue comprises transferring laser energy to the tissue.
 38. The method of claim 37, wherein the laser energy has a wavelength in a range of 400 nanometers to 10.6 micrometers.
 39. The method of claim 38, wherein the laser energy is provided by a continuous wave Holmium:YAG laser.
 40. The method of claim 33, wherein transferring energy from the end effector to the tissue comprises transferring radioactive energy to the tissue.
 41. The method of claim 33, wherein transferring energy from the end effector to the tissue comprises transferring chemical energy to the tissue.
 42. The method of claim 33, wherein transferring energy from the end effector to the tissue comprises transferring mechanical energy to the tissue.
 43. The method of claim 33, wherein transferring energy from the end effector to the tissue comprises elevating a temperature of the tissue to a temperature within a range of 45° C.-75° C.
 44. The method of claim 33, wherein transluminally positioning the end effector comprises percutaneously advancing the apparatus through a patient's venous vasculature.
 45. The method of claim 33, wherein transluminally positioning the end effector comprises percutaneously advancing the apparatus through a patient's arterial vasculature.
 46. The method of claim 33, wherein transluminally positioning the end effector comprises performing a septostomy.
 47. The method of claim 33, further comprising synchronizing energy transfer with a repetitive point in a patient's cardiac cycle.
 48. The method of claim 33, further comprising monitoring flow through the valve during energy transfer. 